<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
  /*
  规则：不能使用关键字、只能用下划线、字母、数字、$组成，且不能以数字开头，字母严格区分大小写
  规范：尽量采取小驼峰或者是大驼峰命名
  * */
  let userName="陶品奇"
  let $password=123456
  let _num=123
  let _NUM=123
  console.log(userName)
  console.log($password)
  console.log(_num)
  console.log(_NUM)
</script>
</body>
</html>